Solid state image sensor, production method thereof and electronic device

ABSTRACT

A solid state image sensor includes a semiconductor substrate where photoelectric conversion regions for converting light into charges are arranged per pixel planarly arranged; an organic photoelectric conversion film laminated at a light irradiated side of the semiconductor substrate via an insulation film and formed at the regions where the pixels are formed; a lower electrode formed at and in contact with the organic photoelectric conversion film at a semiconductor substrate side; a first upper electrode laminated at a light irradiated side of the organic photoelectric conversion film and formed such that ends of the first upper electrode are substantially conform with ends of the organic photoelectric conversion film when the solid state image sensor is planarly viewed; and a film stress suppressor for suppressing an effect of a film stress on the organic photoelectric conversion film, the film stress being generated on the first upper electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2013-189723 filed Sep. 12, 2013, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a solid state image sensor, aproduction method thereof and an electronic device. More particularly,the present disclosure relates to a solid state image sensor, aproduction method thereof and an electronic device for suppressing adark current and a property fluctuation of white flaws of an organicphotoelectric conversion film.

SUMMARY

In the electronic device in the related art having an image capturingfunction such as a digital still camera and a digital video camera, asolid state image sensor such as CCD (Charge Coupled Device) and CMOS(Complementary Metal Oxide Semiconductor) image sensors are used. Thesolid state image sensor has pixels where PDs (photodiodes) forphotoelectric conversion and a plurality of transistors are disposed. Bythe solid state image sensor, images are constructed based on pixelsignals outputted from a plurality of pixels planarly arranged.

In recent years, as a pixel size of the solid state image sensor getssmaller, a photon number (a light amount) incident on a unit pixel isincreased. The sensitivity of pixels may be decreased, which may resultin a decreased S/N (Signal/Noise) ratio.

Currently, there are widely used a solid state image sensor using apixel arrangement where red, green and blue pixels are planarlyarranged, e.g., the Bayer arrangement using a primary color filter. Insuch a solid state image sensor, green and blue colors do not transmitthrough a red pixel that is not used for photoelectric conversion. Theremay result in a loss of the sensitivity. In addition, as a color signalis generated by interpolation between pixels, a false color may begenerated.

In response, there is proposed a solid state image sensor having astructure where three photoelectric conversion layers are laminated in alongitudinal direction, and three color photoelectric conversion signalsare provided in one pixel.

For example, Japanese Patent Application Laid-open No. 2003-332551discloses a solid state image sensor having a photoelectric conversionunit for detecting green light and generating a signal chargecorresponding to the green light disposed above a silicon substrate, andtwo photoelectric conversion regions for detecting blue and red lightslaminated within the silicon substrate.

Furthermore, as one of the solid state image sensors having theabove-described structures, a rear surface irradiation type solid stateimage sensor where a circuit forming surface is formed at an oppositeside of a light receiving plane is proposed.

For example, by a rear surface irradiation type solid state image sensordisclosed in Japanese Patent Application Laid-open No. 2011-29337, aninorganic photoelectric conversion unit and an organic photoelectricconversion unit within a same pixel are brought close each other,thereby suppressing F value dependency of each color and sensitivityfluctuation among the respective colors.

Japanese Patent Application Laid-open No. 2011-228648 discloses an imagesensor that can suppress an occurrence of white spot defects.

As to the solid state image sensor disclosed in the above-describedJapanese Patent Application Laid-open No. 2011-29337, ends of theorganic photoelectric conversion film and the upper electrode areconform. In a heat treatment in the course of manufacture, a film stressof the upper electrode may be locally concentrated on an organicphotoelectric conversion film. Thus, as shown in a relationship betweenthe stress and the white flaws disclosed in Japanese Patent ApplicationLaid-open No. 2011-228648, there is a concern that a dark current and aproperty fluctuation of the white flaws of the organic photoelectricconversion film are dominantly generated.

In view of the circumstances as described above, there is a need forsuppressing a dark current and a property fluctuation of white flaws ofan organic photoelectric conversion film.

According to an embodiment of the present disclosure, there is provideda solid state image sensor, including: a semiconductor substrate wherephotoelectric conversion regions for converting light into charges arearranged per a plurality of pixels planarly arranged; an organicphotoelectric conversion film laminated at a light irradiated side ofthe semiconductor substrate via an insulation film and formed at theregions where a plurality of the pixels are formed; a lower electrodeformed at and in contact with the organic photoelectric conversion filmat a semiconductor substrate side; a first upper electrode laminated ata light irradiated side of the organic photoelectric conversion film andformed such that ends of the first upper electrode are substantiallyconform with ends of the organic photoelectric conversion film when thesolid state image sensor is planarly viewed; and a film stresssuppressor for suppressing an effect of a film stress on the organicphotoelectric conversion film, the film stress being generated on thefirst upper electrode.

According to an embodiment of the present disclosure, there is provideda method of producing a solid state image sensor, including: forming andlaminating an organic photoelectric conversion film on a semiconductorsubstrate via an insulation film at a light irradiated side and at theregions where a plurality of pixels are formed, photoelectric conversionregions for converting light into charges being arranged per a pluralityof the pixels planarly arranged on the semiconductor substrate; forminga lower electrode per the pixels in contact with the organicphotoelectric conversion film at a semiconductor substrate side; forminga first upper electrode laminated at a light irradiated side of theorganic photoelectric conversion film such that ends of the first upperelectrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and forming a film stress suppressor for suppressing aneffect of a film stress on the organic photoelectric conversion film,the film stress being generated on the first upper electrode.

According to an embodiment of the present disclosure, there is providedan electronic device, including: a solid state image sensor, including:a semiconductor substrate where photoelectric conversion regions forconverting light into charges are arranged per a plurality of pixelsplanarly arranged; an organic photoelectric conversion film laminated ata light irradiated side of the semiconductor substrate via an insulationfilm and formed at the regions where a plurality of the pixels areformed; a lower electrode formed at and in contact with the organicphotoelectric conversion film at a semiconductor substrate side; a firstupper electrode laminated at a light irradiated side of the organicphotoelectric conversion film and formed such that ends of the firstupper electrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and a film stress suppressor for suppressing an effectof a film stress on the organic photoelectric conversion film, the filmstress being generated on the first upper electrode.

According to an embodiment of the present disclosure, the organicphotoelectric conversion film is formed and laminated on thesemiconductor substrate via the insulation film at the light irradiatedside and at the regions where a plurality of pixels are formed,photoelectric conversion regions for converting light into charges beingarranged per a plurality of the pixels planarly arranged on thesemiconductor substrate. The lower electrode is formed at and in contactwith the organic photoelectric conversion film at the semiconductorsubstrate side. The first upper electrode is laminated at the lightirradiated side of the organic photoelectric conversion film and formedsuch that the ends of the first upper electrode are substantiallyconform with ends of the organic photoelectric conversion film when thesolid state image sensor is planarly viewed. The film stress suppressorfor suppressing an effect of a film stress on the organic photoelectricconversion film, the film stress being generated on the first upperelectrode.

According to an embodiment of the present disclosure, the propertyfluctuation such as the dark current and the white flaws of the organicphotoelectric conversion film can be suppressed.

These and other objects, features and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription of best mode embodiments thereof, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a first embodiment of a solid stateimage sensor with the application of the present disclosure;

FIG. 2 illustrates a first step of producing the solid state imagesensor shown in FIG. 1;

FIG. 3 illustrates a second step of producing the solid state imagesensor shown in FIG. 1;

FIG. 4 illustrates a third step of producing the solid state imagesensor shown in FIG. 1;

FIG. 5 illustrates a fourth step of producing the solid state imagesensor shown in FIG. 1;

FIG. 6 illustrates a fifth step of producing the solid state imagesensor shown in FIG. 1;

FIG. 7 illustrates a sixth step of producing the solid state imagesensor shown in FIG. 1;

FIG. 8 is a cross-sectional view of a second embodiment of a solid stateimage sensor with the application of the present disclosure;

FIG. 9 is a cross-sectional view of a third embodiment of a solid stateimage sensor with the application of the present disclosure;

FIG. 10 is a cross-sectional view of a fourth embodiment of a solidstate image sensor with the application of the present disclosure; and

FIG. 11 is a block diagram showing a configuration of an imagingapparatus mounted on an electronic device.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be describedwith reference to the drawings.

FIG. 1 is a cross-sectional view of a first embodiment of a solid stateimage sensor with the application of the present disclosure.

A solid state image sensor 11 is configured to have a plurality ofpixels 12 arranged in a planar array. FIG. 1 shows a cross-section whereN numbers of pixels 12-1 to 12-N are arranged. Hereinafter, when thepixels 12-1 to 12-N are interchangeable, it refers to the pixel 12. Thesame applies to each part configuring the pixel 12. Also, in FIG. 1, aplane of the solid state image sensor 11 directed upward is irradiatedwith light. Hereinafter, the plane is referred to as “a light irradiatedplane”, as appropriate. In addition, in FIG. 1, a wiring layer (notshown) is laminated on a plane of the solid state image sensor 11directed downward. Hereinafter, the plane is referred to as “a wiringlayer laminated plane”.

As shown in FIG. 1, the solid state image sensor 11 is configured of asemiconductor substrate 21, insulation films 22 and 23 and an organicphotoelectric conversion film 24 laminated thereon.

Also, each pixel 12 of the solid state image sensor 11 is configured ofphotoelectric conversion regions 31 and 32, a charge buildup region 33,a gate electrode 34, a wiring 35 and a lower electrode 36. In otherwords, a pixel 12-1 is configured of photoelectric conversion regions31-1 and 32-1, a charge buildup region 22-1, a gate electrode 34-1, awiring 35-1 and a lower electrode 36-1. Similarly, a pixel 12-2 isconfigured of photoelectric conversion regions 31-2 and 32-2, a chargebuildup region 22-2, a gate electrode 34-2, a wiring 35-2 and a lowerelectrode 36-2. Hereinafter, the same applies up to the pixel 12-N.

The semiconductor substrate 21 is a silicon wafer where single crystalsof high purity silicon are thin-sliced. At a wiring layer laminatedplane side of the semiconductor substrate 21, a plurality of transistors(not shown) (for example, a transfer transistor, an amplifiertransistor, a selection transistor and reset transistor) are formed.Furthermore, on a peripheral region around the pixel 12 of thesemiconductor substrate 21, a peripheral circuit (not shown) such as alogic circuit is formed. On the wiring layer laminated plane of thesemiconductor substrate 21, a multilayer wiring layer where a pluralityof wiring layers are arranged via interlayer insulation films islaminated. On the multilayer wiring layer, a support substrate (notshown) for supporting the thin semiconductor substrate 21 is adhered.

The insulation film 22 is for insulating the light irradiated plane ofthe semiconductor substrate 21. As the insulation film 22, a film havinga low interface state is desirable in order to decrease the interfacestate between the insulation film 22 and the semiconductor substrate 21and to suppress a dark current from the interface between thesemiconductor substrate 21 and the insulation film 22.

The insulation film 23 is for insulating the lower electrodes 36, and isa SiO₂ (silicon dioxide) film, for example.

In the organic photoelectric conversion layer 24, an organicphotoelectric conversion film 37, a first upper electrode 38 and asecond upper electrode 39 are laminated to cover the region where aplurality of pixels 12 are arranged. A passivation film 40 is whollyformed. A wiring 41 is connected to the second upper electrode 39.

The photoelectric conversion regions 31 and 32 are formed to belaminated in a depth direction (a top and bottom direction in FIG. 1)within the semiconductor substrate 21. For example, the photoelectricconversion regions 31 photoelectrically convert blue light. Thephotoelectric conversion regions 32 formed at a deeper position than thephotoelectric conversion regions 31 (far from the light irradiatedplane) photoelectrically convert red light.

Each charge buildup region 33 is formed within the semiconductorsubstrate 21 at the wiring layer laminated plane side, and is connectedto each lower electrode 36 via each wiring 35. The charge buildup region33 builds up charges that are photoelectrically converted at a part ofthe organic photoelectric conversion film 37 connected and disposedbetween the lower electrode 36 and the upper electrode 38. The chargesbuilt up in the charge buildup region 33 are applied to a gate electrodeof the amplifier transistor (not shown) via the transfer transistorconfigured of the gate electrode 34.

Each gate electrode 34 is laminated on a surface of the wiring layerlaminated plane of the semiconductor substrate 21, and configures thetransfer transistor that transfers the charges accumulated on the chargebuildup region 33, for example.

Each wiring 35 connects each charge buildup region 33 to each lowerelectrode 36 per pixel 12. Also, each wiring 35 acts as a lightshielding film that shields light on the region between the pixels 12,for example.

Each lower electrode 36 is formed at and in contact with the organicphotoelectric conversion film 37 at a semiconductor substrate side 21.As described above, the lower electrodes 36 of the respective pixels 12are insulated each other by the insulation film 23.

The organic photoelectric conversion film 37 is composed of an organicmaterial as described later, performs the photoelectric conversion, andis laminated on an entire surface of the regions where the pixels 12 arearranged. For example, the organic photoelectric conversion film 37photoelectrically converts green light.

The first upper electrode 38 is laminated on the organic photoelectricconversion film 37, and is formed such that ends of the first upperelectrode 38 is substantially conform with ends of the organicphotoelectric conversion film 37 when the solid state image sensor 11 isplanarly viewed.

The second upper electrode 39 is laminated on the first upper electrode38 at a region greater than a region where the first upper electrode 38is formed, i.e., across the first upper electrode 38 to connect aperipheral region of the second upper electrode 39 to the insulationfilm 23. In this way, the second upper electrode 39 is formed to pressthe first upper electrode 38, thereby suppressing an effect of a filmstress on the ends of the organic photoelectric conversion film 37. Thefilm stress is generated on the first upper electrode 38 in a laterheating step. For example, even though the film stress such as bendingbackward is generated on the first upper electrode 38, the peripheralregion of the second upper electrode 39 is connected to the insulationfilm 23, whereby the second upper electrode 39 can suppress the bendingbackward of the first upper electrode 38.

The passivation film 40 is for protecting the surface of the solid imagesensor 11.

The wiring 41 is connected to an external circuit (not shown) in orderto apply a predetermined potential to the first and second upperelectrodes 38 and 39.

In the solid state image sensor 11 configured in this way, among thelights irradiated from an upper side in FIG. 1, green light isphotoelectrically converted in the organic photoelectric conversion film37, blue light is photoelectrically converted in the photoelectricconversion regions 32, and red light is photoelectrically converted inthe photoelectric conversion regions 31. Then, the second upperelectrode 39 can suppress the effect of the film stress generated on thefirst upper electrode 38 on the ends of the organic photoelectricconversion film 37. Thus, the film stress on the organic photoelectricconversion film 37 can be uniform, and the property fluctuation such aswhite flaws of the organic photoelectric conversion film 37 and the darkcurrent can be suppressed.

The solid state image sensor 11 can avoid light loss by using a colorfilter and can provide a higher photoelectric conversion efficiencycompared to, for example, a solid image sensor utilizing the Bayerarrangement using a primary color filter.

Next, referring to FIGS. 2 to 7, a method of producing a solid stateimage sensor 11 will be described.

Firstly, in a first step, the photoelectric conversion regions 31 and 32are formed within the semiconductor substrate 21 that is not thinned, asshown in FIG. 2. At the wiring layer laminated plane side of thesemiconductor substrate 21, the charge buildup region 33 is formed. Onthe surface of the wiring layer laminated plane of the semiconductorsubstrate 21, the gate electrodes 34 and so on are laminated via theinsulation film (not shown). A plurality of the pixel transistorsincluding the transfer transistor are formed.

Then, a peripheral circuit (not shown) is formed on the semiconductorsubstrate 21. The multilayer wiring layer (not shown) is laminated onthe wiring layer laminated plane of the semiconductor substrate 21. Tothe multilayer wiring layer, the support substrate is adhered.Thereafter, silicon and a silicon oxide film at a light irradiated planeside of the semiconductor substrate 21 are removed. This allows to thinthe semiconductor substrate 21 as shown in FIG. 2 and to expose thelight irradiated plane of the semiconductor substrate 21 (in otherwords, a rear surface of the semiconductor substrate 21 when the sidewhere the multilayer wiring layer and the support substrate arelaminated is defined as the surface).

Next, in a second step, the insulation film 22 is laminated on the lightirradiated plane of the semiconductor substrate 21, as shown in FIG. 3.For example, as the insulation film 22, a lamination structure of ahafnium oxide (HfO₂) film formed by an ALD (Atomic Layer Deposition)method and a plasma CVD (Chemical Vapor Deposition) method. Thestructure and the film forming method of the insulation film 22 are notlimited thereto.

Next, in a third step, as shown in FIG. 4, there are formed throughholes that pass through the semiconductor substrate 21 and theinsulation film 22 from the light irradiated plane side to the chargebuildup regions 33, and the through holes are buried with a conductivematerial to form the wirings 35. As the material for the wirings 35, alight shielding material is used. The surface of the insulation film 22is processed to leave a region to be light-shielded. For example, alaminated film of barrier metal titanium (Ti) and titanium nitride (TiN)and tungsten (W) are desirably used. However, the structure and thematerial of the wirings 35 are not limited thereto.

In this step, the lower electrodes 36 are formed. As the light has to bepassed through the lower electrodes 36, the lower electrodes 36 areformed by sputtering ITO (Indium Tin Oxide), patterning using aphotolithography technique, and processing by dry or wet etching. Uponthe formation of the lower electrodes 36, the insulation film 23 thatelectrically insulates the lower electrodes 36 is formed. For example,the insulation layer 23 is an SiO₂ film formed by a plasma CVD methodbetween the lower electrodes 36, and is planarized by a CMP (ChemicalMechanical Polishing).

As the material of the lower electrodes 36, it is not limited to theabove-described ITO, and tin oxide-based SnO₂ (dopant added) can also beused. In addition, as the material of the lower electrodes 36, a zincoxide-based material can be used. Examples of the zinc oxide-basedmaterial include aluminum zinc oxide (Al is added as a dopant to ZnO,e.g., AZO), gallium zinc oxide (Ga is added as a dopant to ZnO, e.g.,GZO) and indium zinc oxide (In is added as a dopant to ZnO, e.g., IZO).Furthermore, as the material of the lower electrodes 36, IGZO, CuI,InSbO₄, ZnMgO, CuInO₂, MgIn₂O₄, CdO, ZnSnO₃ and the like can be used.

In the third step, the lower electrodes 36 are connected to the chargebuildup regions 33 via the wirings 35. The wirings 35 and the lowerelectrodes 36 may be patterned, whichever may be patterned first.

Next, in a fourth step, as shown in FIG. 5, the material for the organicphotoelectric conversion film 37 is formed on an entire surface of theinsulation film 23 and the lower electrodes at the light irradiatedplane side. On an entire surface of the film 37, the material for thefirst upper electrode 38 is film-formed.

The organic photoelectric conversion film 37 is formed usingquinacridone by a vacuum deposition method. The organic photoelectricconversion film 37 includes a structure where an electron blocking andbuffer film, a photoelectric conversion film, a hole blocking film, ahole blocking and buffer film and a work function adjustment film arelaminated on the lower electrodes 36. Specifically, the organicphotoelectric conversion film 37 includes a structure having at leastone of an organic p type semiconductor and an organic n typesemiconductor. More desirably, as shown in FIG. 5, it is desirable thata pin bulk hetero structure including a p type blocking layer 37 a, a pand n type codeposition phase (i phase) 37 b, and an n type blockinglayer 37 c.

As the organic p type semiconductor and an n type semiconductor for theorganic photoelectric conversion film 37, any of a quinacridonederivative, a naphthalene derivative, an anthracene derivative, aphenanthrene derivative, a tetracene derivative, a pyrene derivative, aperylene derivative and a Fluoranthene derivative can be desirably used.Also, a phenylene vinylene, fluorine, carbazole, indole, pyrene, pyroll,picoline, thiophene, acetylene or diacetylene polymer or a derivativethereof can be used. Furthermore, a chain compound where a fusedpolycyclic aromatic and aromatic ring or heterocyclic ring compound arefused such as a metal complex pigment, a cyanine-based pigment, amerocyanine-based pigment, a phenyl xanthene-based pigment, a triphenylmethane-based pigment, a Rhoda cyanine-based pigment, a xanthene-basedpigment, a macrocyclic azaanuulene-based pigment, an azulene-basedpigment, naphthoquinone, an anthraquinone-based pigment, anthracene andpyrene; a cyanine-based analog pigment bonded by two nitrogen-containinghetero rings such as quinolone, benzothiazole and benzooxazole having asquarylium group and a croco nick methane group as a bonding group or bya squarylium group and a croco nick methane group.

As the above-described metal complex pigment, a dithiol metalcomplex-based pigment, a metal phthalocyanine-based pigment, a metalporphyrin-based pigment or a ruthenium complex pigment is desirable. Theruthenium complex pigment is most desirable. The material for theorganic photoelectric conversion film 37 is not limited to the above.The organic photoelectric conversion film 37 may be formed by coating.

The first upper electrode 38 has to be transparent to the visible light,and is formed of ITO by sputtering, for example. As is generally known,the properties of the first upper electrode 38 are greatly changed dueto effects of moisture, oxygen and hydrogen. It is therefore desirableto form the first upper electrode 38 in a multi-chamber together withthe organic photoelectric conversion film 37. In order to prevent theorganic photoelectric conversion film 37 from changing by theultraviolet rays applied in the production, the first upper electrode 38is desirably formed of the material that absorbs the ultraviolet rayshaving a wavelength of 400 nm or less.

The material of the first upper electrode 38 is not limited to theabove-described ITO, and may be formed of tin oxide-based SnO₂ (dopantadded). In addition, as the material of the first upper electrode 38, asa zinc oxide-based material, aluminum zinc oxide (Al is added as adopant to ZnO, e.g., AZO), gallium zinc oxide (Ga is added as a dopantto ZnO, e.g., GZO) and indium zinc oxide (In is added as a dopant toZnO, e.g., IZO) can be used. Furthermore, as the material of the upperelectrode 38, IGZO, CuI, InSbO₄, ZnMgO, CuInO₂, MgIn₂O₄, CdO, ZnSnO₃ andthe like can be used.

Next, in the fifth step, as shown in FIG. 6, the first upper electrode38 and the organic photoelectric conversion film 37 are processed suchthat the ends of the first upper electrode 38 is substantially conformwith the ends of the organic photoelectric conversion film 37. Forexample, the first upper electrode 38 and the organic photoelectricconversion film 37 are processed by patterning using a photolithographytechnique to leave the regions where the pixels 12 are formed, and dryetching to remove other regions the regions where the pixels 12 areformed. Then, post processing such as ashing and organic cleaning isperformed to remove deposition and residues.

Next, in a sixth step, as shown in FIG. 7, the second upper electrode 39is formed. For example, the material for the second upper electrode 39is formed on an entire surface of the first upper electrode 38 and theinsulation film 23. Then, the second upper electrode 39 is processed bypatterning using a photolithography technique such that ends of thesecond upper electrode 39 extend exceeding the ends of the first upperelectrode 38 and then by dry etching.

Here, it is desirable that the same material is used for the first andsecond upper electrodes 38 and 39. For the second upper electrode 39,there may be used a material which is transparent to the visible lightand has the properties (the film stress and a coefficient of thermalexpansion) similar to (substantially the same as) those of the materialfor the first upper electrode 38.

Thereafter, the wiring 41 for electrically connect the first and secondupper electrodes 38 and 39 to the external is formed, and thepassivation film 40 is formed, there by producing the solid state imagesensor 1 shown in FIG. 1.

As a material for the wiring 41, tungsten (W), titanium (Ti), titaniumnitride (TiN), aluminum (Al) or the like can be used, for example. Forthe wiring 41, other material having conductivity may be used. Thewiring 41 is formed by patterning using a photolithography technique andprocessing by dry etching. Then, post processing such as ashing andorganic cleaning is performed to remove deposition and residues.

After the passivation film 40 is formed, a planarized film, an on-chiplens and the like (not shown) are formed.

As described above, even if the solid state image sensor 11 has aconfiguration that the ends of the organic photoelectric conversion film37 are conform with the ends of the first upper electrode 38, theperipheral region of the second upper electrode 39 is formed so as toconnect to the insulation film 23, whereby the film stress generated onthe first upper electrode 38 in the later heating step is prevented fromaffecting on the organic photoelectric conversion film 37. In this way,the solid state image sensor 11 can be produced without fluctuating theproperties including the dark current and the white flaws of the organicphotoelectric conversion film 37.

Also as described above, the organic photoelectric conversion film 37 ispatterned by a photolithography technique and dry etching, therebyperforming a microfabrication easily. Thus, the pixels 12 in the solidstate image sensor 11 can be small-sized.

Next, referring to FIG. 8, a second embodiment of a solid state imagesensor will be described. As to a solid state image sensor 11A shown inFIG. 8, the components common to the solid state image sensor 11 shownin FIG. 1 are denoted by the same reference numerals, and thus detaileddescription thereof will be hereinafter omitted.

As shown in FIG. 8, the solid state image sensor 11A has the sameconfiguration as that of the solid state image sensor 11 shown in FIG. 1with respect to the semiconductor substrate 21 and the insulation films22 and 23. However, an organic photoelectric conversion layer 24A of thesolid state image sensor 11A is different from the organic photoelectricconversion layer 24 of the solid state image sensor 11 shown in FIG. 1.

In other words, in the organic photoelectric conversion layer 24A of thesolid state image sensor 11A, an insulation film 51 is formed betweenthe first upper electrode 38 and the second upper electrode 39. For theinsulation film 51, silicon nitride (SiN) is used, for example. Afterthe first upper electrode 38 is formed (the fourth step as describedabove referring to FIG. 5), the material for the insulation film 51 isformed on an entire surface of the first upper electrode 38. Then, theinsulation film 51 is processed together with the organic photoelectricconversion film 37 and the first upper electrode 38 (the fifth step asdescribed above referring to FIG. 6).

Here, the insulation film 51 is transparent to the visible light andshould have an ultraviolet ray absorbing property. As the material forthe insulation film 51, SiN, SiO₂, SiON, AlO, AlN and the like can beused. The conditions for an SiN film formation using a CVD method are: aparallel plate plasma CVD apparatus is used at an RF power of 500 W, asubstrate temperature of 200° C., a pressure of 5 Torr, N₂ flow rate of500 sccm, SiH₄ flow rate of 500 sccm and NH₃ flow rate of 100 sccm. TheSiN film formed under the conditions absorbs ultraviolet rays. It isdesirable that the insulation film 51 absorb all or a part of thewavelength of 400 nm or less and have a transmittance of 80% or more.The insulation film 51 may have a thickness of about 10 nm to 500 nm.

In FIG. 8, as the insulation film 51, a monolayer film structure such asan SiN or SiON film is shown. However, a multilayer structure having twoor more layers may be used. Also, as the material for the insulationfilm 51, a metal oxide such as titanium oxide, vanadium oxide andchromium oxide can be used, which provides a similar effect.

Also in the solid state image sensor 11A thus configured similar to thesolid state image sensor 11, the film stress on the organicphotoelectric conversion film 37 can be uniform, and the propertyfluctuation such as white flaws and the dark current can be suppressed.In addition, as the insulation film 51 is formed in the solid stateimage sensor 11A, the ultraviolet rays can be absorbed.

Next, referring to FIG. 9, a third embodiment of a solid state imagesensor will be described. As to a solid state image sensor 11B shown inFIG. 9, the components common to the solid state image sensor 11 shownin FIG. 1 are denoted by the same reference numerals, and thus detaileddescription thereof will be hereinafter omitted.

As shown in FIG. 9, the solid state image sensor 11B has the sameconfiguration as that of the solid state image sensor 11 shown in FIG. 1with respect to the semiconductor substrate 21 and the insulation films22 and 23. However, an organic photoelectric conversion layer 24B of thesolid state image sensor 11B is different from the organic photoelectricconversion layer 24 of the solid state image sensor 11 shown in FIG. 1.

In other words, in the organic photoelectric conversion layer 24B of thesolid state image sensor 11B, an insulation film 51 is laminated on thefirst upper electrode 38, and a second upper electrode 39B is formedonly outside of the ends of the first upper electrode 38. In otherwords, the second upper electrode 39B is formed around an outerperiphery of the first upper electrode 38 to connect the ends of thefirst upper electrode 38 and the insulation film 23. In the solid stateimage sensor 11B, after the insulation film 51 is formed and the secondupper electrode 39 is formed similar to the case of the solid stateimage sensor 11A shown in FIG. 8, the region of the second upperelectrode 39 disposed above of the insulation film 51 is removed to formthe second upper electrode 39B.

Also in the solid state image sensor 11B thus configured similar to thesolid state image sensor 11, the film stress on the organicphotoelectric conversion film 37 can be uniform, and the propertyfluctuation such as white flaws and the dark current can be suppressed.In addition, as the insulation film 51 is formed in the solid stateimage sensor 11B, the ultraviolet rays can be absorbed. The second upperelectrode 39B is formed only around the outer periphery of the firstupper electrode 38. This allows to thin the organic photoelectricconversion layer 24B.

Next, referring to FIG. 10, a fourth embodiment of a solid state imagesensor will be described. As to a solid state image sensor 11C shown inFIG. 10, the components common to the solid state image sensor 11 shownin FIG. 1 are denoted by the same reference numerals, and thus detaileddescription thereof will be hereinafter omitted.

As shown in FIG. 10, the solid state image sensor 11C has the sameconfiguration as that of the solid state image sensor 11 shown in FIG. 1with respect to the semiconductor substrate 21 and the insulation films22 and 23. However, an organic photoelectric conversion layer 24C of thesolid state image sensor 11C is different from the organic photoelectricconversion layer 24 of the solid state image sensor 11 shown in FIG. 1.

In other words, in the organic photoelectric conversion layer 24C of thesolid state image sensor 11C, ends of the organic photoelectricconversion film 37, the first upper electrode 38 and a stress adjustmentinsulation film 53, which form a laminated layer, are substantiallyconform with each other. The film stress of the insulation film 51 iscontrolled to provide a substantially uniform film stress of thelaminated film over an entire surface (for example, neutral at ±200MPa).

Specifically, after the organic photoelectric conversion film 37 isformed similar to the above-described production method, the first upperelectrode 38 is formed. The first upper electrode 38 is formed by asputtering method. The ITO film is formed by the conditions: an RFsputtering apparatus is used at an RF power of 800 W, a substratetemperature of 20° C., a pressure of 0.2 Torr Ar flow rate of 15 sccm.For example, by controlling the film formation conditions including theRF power, an ITO film stress can be controlled.

Thereafter, the stress adjustment insulation film 53 made of SiN isformed. For example, the stress adjustment insulation film 53 is formedby patterning using a photolithography technique and processing by dryetching. Then, post processing such as asking and organic cleaning isperformed to remove deposition and residues.

Here, the stress adjustment insulation film 53 is transparent to thevisible light and should have an ultraviolet ray absorbing propertysimilar to the insulation film 51 as described referring to FIG. 8. Asthe material for the stress adjustment insulation film 53, SiN, SiO₂,SiON, AlO, AlN and the like can be used. The conditions for an SiN filmformation using a CVD method are: a parallel plate plasma CVD apparatusis used at an RF power of 500 W, a substrate temperature of 200° C., apressure of 5 Torr, N₂ flow rate of 500 sccm, SiH₄ flow rate of 500 sccmand NH₃ flow rate of 100 sccm. As to the stress adjustment insulationfilm 53, by controlling the film formation conditions including the RFpower, the film stress can be controlled.

As described above, by controlling the conditions for forming the firstupper electrode 38 and the stress adjustment insulation film 53, thefilm stress can be neutral (±200 MPa, + denotes compression and −denotes a direction of tensile stress) when the first upper electrode 38and the stress adjustment insulation film 53 are laminated. In this way,similar to the solid state image sensor 11 shown in FIG. 1, in the solidstate image sensor 11C, the film stress on the organic photoelectricconversion film 37 can be uniform, and the property fluctuation such aswhite flaws and the dark current can be suppressed.

The present disclosure can be applied not only to the solid state imagesensor 11 having the configuration that the photoelectric conversionregions 31 and 32 are formed within the semiconductor substrate 21 andthe organic photoelectric conversion film 37 is formed at the lightirradiated plane side of the semiconductor substrate 21, but also tosolid state image sensors having other configurations. In addition, thepresent disclosure can be applied not only to a rear surface (i.e., arear surface opposite to a surface of the semiconductor substrate 21where the multilayer wiring layer and the support substrate arelaminated) irradiation type solid state image sensor where a rearsurface of the solid state image sensor 11 is irradiated with light, butalso to other solid state image sensors including a surface irradiatedtype solid state image sensor.

The solid state image sensor 11 according to the above-describedembodiments can be applied to a variety of electronic devices includingan image capturing system such as a digital still camera and digitalvideo camera, a mobile phone having an image capturing function andother devices having an image capturing function.

FIG. 11 is a block diagram showing a configuration of an imagingapparatus mounted on an electronic device.

As shown in FIG. 11, an image capturing apparatus 101 is configured tohave an optical system 102, an image capturing element 103, a signalprocessing circuit 104, a monitor 105 and a memory 106, and can capturestill images and moving images.

The optical system 102 is configured to have one or more lenses, leadsimage light (incident light) from an object to be captured to the imagecapturing element 103, and captures the image light on a light receivingplane (a sensor unit) of the image capturing element 103.

To the image capturing element 103, the solid state image sensor 11according to the above-described embodiments is applied. In the imagecapturing element 103, electrons are accumulated for a predeterminedduration depending on the image captured on the light receiving planevia the optical system 102. A signal corresponding to the electronsaccumulated on the image capturing element 103 is fed to the signalprocessing circuit 104.

The signal processing circuit 104 processes a pixel signal outputtedfrom the image capturing element 103 in various ways. By the signalprocessing of the signal processing circuit 104, the resultant image(image data) is fed to and displayed on the monitor 105 or fed to andstored (recorded).

By applying the solid state image sensor 11 according to theabove-described embodiments, the image capturing apparatus 101 thusconfigured can provide high quality images, for example.

The present disclosure may have the following configurations.

(1) A solid state image sensor, including:

a semiconductor substrate where photoelectric conversion regions forconverting light into charges are arranged per a plurality of pixelsplanarly arranged;

an organic photoelectric conversion film laminated at a light irradiatedside of the semiconductor substrate via an insulation film and formed atthe regions where a plurality of the pixels are formed;

a lower electrode formed at and in contact with the organicphotoelectric conversion film at a semiconductor substrate side;

a first upper electrode laminated at a light irradiated side of theorganic photoelectric conversion film and formed such that ends of thefirst upper electrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and

a film stress suppressor for suppressing an effect of a film stress onthe organic photoelectric conversion film, the film stress beinggenerated on the first upper electrode.

(2) The solid state image sensor according to (1) above, in which

the film stress suppressor is a second upper electrode laminated at alight irradiated side of the first upper electrode, and the second upperelectrode is formed on the first upper electrode at a region greaterthan a region where the first upper electrode is formed to connect aperipheral region of the second upper electrode to the insulation film.

(3) The solid state image sensor according to (2) above, in which

the first upper electrode and the second upper electrode are formed of asame material or a material having a substantially same property.

(4) The solid state image sensor according to any one of (1) to (3)above, further including:

a second insulation film laminated on the first upper electrode suchthat ends of the organic photoelectric conversion film and the firstupper electrode are substantially conformed.

(5) The solid state image sensor according to any one of (1) to (4)above, in which

the film stress suppressor is formed around an outer periphery of thefirst upper electrode to connect the ends of the first upper electrodeand the insulation film.

(6) The solid state image sensor according to any one of (1) to (5)above, in which

the film stress suppressor is a stress adjustment insulation filmlaminated on the first upper electrode such that ends of the first upperelectrode is substantially conform with the stress adjustment insulationfilm, and the stress adjustment insulation film is formed under thecondition that the film stress generated on the first upper electrodebecomes substantially uniform.

(7) A method of producing a solid state image sensor, including:

forming and laminating an organic photoelectric conversion film on asemiconductor substrate via an insulation film at a light irradiatedside and at the regions where a plurality of pixels are formed,photoelectric conversion regions for converting light into charges beingarranged per a plurality of the pixels planarly arranged on thesemiconductor substrate;

forming a lower electrode per the pixels in contact with the organicphotoelectric conversion film at a semiconductor substrate side;

forming a first upper electrode laminated at a light irradiated side ofthe organic photoelectric conversion film such that ends of the firstupper electrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and

forming a film stress suppressor for suppressing an effect of a filmstress on the organic photoelectric conversion film, the film stressbeing generated on the first upper electrode.

(8) An electronic device, including:

-   -   a solid state image sensor, including:        -   a semiconductor substrate where photoelectric conversion            regions for converting light into charges are arranged per a            plurality of pixels planarly arranged;        -   an organic photoelectric conversion film laminated at a            light irradiated side of the semiconductor substrate via an            insulation film and formed at the regions where a plurality            of the pixels are formed;        -   a lower electrode formed at and in contact with the organic            photoelectric conversion film at a semiconductor substrate            side;        -   a first upper electrode laminated at a light irradiated side            of the organic photoelectric conversion film and formed such            that ends of the first upper electrode are substantially            conform with ends of the organic photoelectric conversion            film when the solid state image sensor is planarly viewed;            and        -   a film stress suppressor for suppressing an effect of a film            stress on the organic photoelectric conversion film, the            film stress being generated on the first upper electrode.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A solid state image sensor, comprising: asemiconductor substrate where photoelectric conversion regions forconverting light into charges are arranged per a plurality of pixelsplanarly arranged; an organic photoelectric conversion film laminated ata light irradiated side of the semiconductor substrate via an insulationfilm and formed at the regions where a plurality of the pixels areformed; a lower electrode formed at and in contact with the organicphotoelectric conversion film at a semiconductor substrate side; a firstupper electrode laminated at a light irradiated side of the organicphotoelectric conversion film and formed such that ends of the firstupper electrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and a film stress suppressor for suppressing an effectof a film stress on the organic photoelectric conversion film, the filmstress being generated on the first upper electrode.
 2. The solid stateimage sensor according to claim 1, wherein the film stress suppressor isa second upper electrode laminated at a light irradiated side of thefirst upper electrode, and the second upper electrode is formed on thefirst upper electrode at a region greater than a region where the firstupper electrode is formed to connect a peripheral region of the secondupper electrode to the insulation film.
 3. The solid state image sensoraccording to claim 2, wherein the first upper electrode and the secondupper electrode are formed of a same material or a material having asubstantially same property.
 4. The solid state image sensor accordingto claim 1, further comprising: a second insulation film laminated onthe first upper electrode such that ends of the organic photoelectricconversion film and the first upper electrode are substantiallyconformed.
 5. The solid state image sensor according to claim 1, whereinthe film stress suppressor is formed around an outer periphery of thefirst upper electrode to connect the ends of the first upper electrodeand the insulation film.
 6. The solid state image sensor according toclaim 1, wherein the film stress suppressor is a stress adjustmentinsulation film laminated on the first upper electrode such that ends ofthe first upper electrode is substantially conform with the stressadjustment insulation film, and the stress adjustment insulation film isformed under the condition that the film stress generated on the firstupper electrode becomes substantially uniform.
 7. A method of producinga solid state image sensor, comprising: forming and laminating anorganic photoelectric conversion film on a semiconductor substrate viaan insulation film at a light irradiated side and at the regions where aplurality of pixels are formed, photoelectric conversion regions forconverting light into charges being arranged per a plurality of thepixels planarly arranged on the semiconductor substrate; forming a lowerelectrode per the pixels in contact with the organic photoelectricconversion film at a semiconductor substrate side; forming a first upperelectrode laminated at a light irradiated side of the organicphotoelectric conversion film such that ends of the first upperelectrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and forming a film stress suppressor for suppressing aneffect of a film stress on the organic photoelectric conversion film,the film stress being generated on the first upper electrode.
 8. Anelectronic device, comprising: a solid state image sensor, comprising: asemiconductor substrate where photoelectric conversion regions forconverting light into charges are arranged per a plurality of pixelsplanarly arranged; an organic photoelectric conversion film laminated ata light irradiated side of the semiconductor substrate via an insulationfilm and formed at the regions where a plurality of the pixels areformed; a lower electrode formed at and in contact with the organicphotoelectric conversion film at a semiconductor substrate side; a firstupper electrode laminated at a light irradiated side of the organicphotoelectric conversion film and formed such that ends of the firstupper electrode are substantially conform with ends of the organicphotoelectric conversion film when the solid state image sensor isplanarly viewed; and a film stress suppressor for suppressing an effectof a film stress on the organic photoelectric conversion film, the filmstress being generated on the first upper electrode.